The present invention relates to an apparatus for producing medical grade, highly fluid, sterile ice slurry capable of being delivered at high ice particle loadings through specially designed medical delivery tubing and insertion devices. Appropriate slurry delivery tubing and insertion devices are described in co pending patent application Ser. No. 11/038,570 entitled “Phase-Change Particulate Ice Slurry Coolant Medical Delivery Tubing and Insertion Devices” filed on Jan. 1, 2005, the entire teaching of which is incorporated herein by reverence.
Inducing hypothermia has been used as a technique for improving neurological and cardiovascular function following medical emergencies such as cardiac arrest, stroke, myocardial infarction, and the like. Cooling an organ reduces its metabolic demand, which dramatically enhances the ability of cells to survive severe oxygen deprivation, ischemia. Application of phase change particulate ice slurries to targeted organs has proved to be an effective method of inducing protective hypothermia. For example, U.S. Pat. No. 6,547,811 and pending U.S. patent application Ser. No. 10/162,442 filed Jun. 3, 2002 both entitled “Method of Inducing Hypothermia,” and both incorporated herein by reference, teach the use of ice slurry to cool parts of the body in order to induce protective hypothermia during for example medical emergencies. Recently the application of protective organ cooling has been expanded to surgical procedures and other medical uses. For example, co-pending patent application Ser. No. 11/140,500 entitled “Ice Slurries and Method Using,” filed May 27, 2005, the teaching of which is also incorporated herein by reference, discloses a number of applications where induced hypothermia through targeted cooling of various organs provides significant medical benefits. In the surgical setting, inducing hypothermia to counter the damaging effects of ischemia provides a viable option for protecting targeted organs, such as the brain, heart, kidneys, liver, or pancreas against oxygen deprivation resulting from obstructions in blood flow.
According to the invention describe in the “Ice Slurries and Method of Using” patent application, hypothermia is induced in targeted organs by delivering a two phase ice slurry directly to the targeted organ via specially designed tubing and injection devices. Because of the inherently higher amount of energy required to melt ice (heat of fusion for phase change 80 cal/g) rather than to warm chilled water (1 cal/g° C.), the cooling capacity of highly loaded ice slurry is many times greater than that of conventional chilled single-phase saline coolants. This reduces both the volume of coolant and the amount of time necessary to cool organs to the desired temperature. Furthermore, once fully melted in the body, ice slurry resembles basic medical-grade saline solution with a standard 0.9% salt concentration.
In order to successfully deliver the ice slurry to the targeted organs or other areas of the body the slurry itself must possess a number of important characteristics. First, the ice particles within the slurry must be small (<0.1 mm) and relatively smooth. Rough dendritic particles tend to become tangled up with one another leading to clogging in the delivery tubing or the insertion devices. Secondly, the saline solution from which the slurry is produced must be biologically compatible and sterile. Medical drip bag saline is preferred. The ice slurry must also be highly fluid and easily pumpable to avoid plugging delivery tubing and pumps. And finally, in order to achieve the most efficient cooling with a minimal amount of slurry, to avoid over loading of organs and other subsystems with coolant, high ice particle loading concentrations are desirable.
The present invention provides an apparatus and method for efficiently producing medical grade ice slurries for cooling targeted organs and other areas of the body.